Field of the Invention
The present invention relates to cellobiohydrolase variants, polynucleotides encoding the variants, and methods of producing and using the variants.
Description of the Related Art
Cellulose is a polymer of the simple sugar glucose covalently linked by beta-1,4-bonds. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases.
Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the lignocellulose is converted to fermentable sugars, e.g., glucose, the fermentable sugars can easily be fermented by yeast into ethanol.
WO 2011/050037 discloses Thielavia terrestris cellobiohydrolase variants with improved thermostability. WO 2011/050037 discloses Aspergillus fumigatus cellobiohydrolase variants with improved thermostability. WO 2005/028636 discloses variants of Hypocrea jecorina Cel7A cellobiohydrolase I. WO 2005/001065 discloses variants of Humicola grisea Cel7A cellobiohydrolase I, Hypocrea jecorina cellobiohydrolase I, and Scytalidium thermophilium cellobiohydrolase I. WO 2004/016760 discloses variants of Hypocrea jecorina Cel7A cellobiohydrolase I. U.S. Pat. No. 7,375,197 discloses variants of Trichoderma reesei cellobiohydrolase I.
There is a need in the art for cellobiohydrolase variants with improved properties to increase the efficiency of the saccharification of lignocellulosic feedstocks.
The present invention provides cellobiohydrolase variants with increased specific performance, polynucleotides encoding the variants, and methods of producing and using the variants.